Since you like the practices that this farm close to you follows, Long Dream Farm, maybe you can do an internship there and get some real day to day experience on what they do and how they do it. That would give you both some practical experience and some lessons in the expense end of it too.
I raise some jerseys and guernseys and use them as nurse cows and to milk. I like tame and mostly friendly cows as they are usually easier to work with. However, making them too friendly or too tame can also have a downside because they lose the respect for you that is necessary for day to day interaction. They are still cows as everyone has said, and they have to have some respect for you or you can get hurt. They can hurt you from just pushing and shoving due to their size and not from them being mean or unmanageable.
I would really encourage you to spend some time on a working farm to get a good feel for what you are trying to do. I am all for cattle that are friendly and manageable and I do not like or believe in being cruel to any animal regardless of the breed. There is a line though and in this day and age unless you are independently wealthy, you can not justify the costs of keeping an animal just as a pet. And when they have outlived their productive life, there is a time when you have to make decisions. I have buried several of our "old cows" over the years as they were good cows and deserved to live their last few months/years out on our place. But, most people who buy an animal, and have $1,000 to 3,000 tied up in them, can not afford to just bury them, but will need to salvage some of their investment back and to be able to invest in a replacement, or to just recoup some of that original investment. Most people who are looking for a family type cow, for milk, are not able to just let that investment die of old age without getting something back out of it. They are usually getting that animal to try to save themselves some money in the costs of milk and beef, and the calves off that animal are raised and eaten, or raised and sold to offset the cost of having that animal.
The dairy industry being what it is, having your own animal is seen as desireable to many people but they still have to justify the costs.